Cupuaçu seeds
Biodiesel
Ethanolysis
Statistical optimization Central composite design Response surface methodology
1. Introduction
Biodiesel has attracted a lot of attention as a promising substitute for conventional diesel because of its attractive features. It is renewable, biodegradable, non-toxic, carbon neutral, emits low exhaust emissions, has a higher flash point and excellent lubricity and is also en- vironmentally acceptable in diesel engines without the need for many engine changes [1,2].
The starting materials for the preparation of biodiesel are vegetable oils or animal fats and alcohol for producing alkyl esters of fatty acids. It is worth noting that most of the studies on biodiesel synthesis prefer to use the methanolysis route, since the size of the alcohol chain greatly influences the conversion percentage [3,4]. However, based on cost and performance considerations, the ethanol can be obtained from renew- able agricultural resources, it is non-toxic and it forms stable fatty acid esters [5,6]. Therefore, better suited for the production of this biofuel.
Biodiesel synthesis is usually catalyzed by homogeneous, hetero- geneous or enzymatic processes, as well as supercritical technology [7,8]. There are several methods for producing the biofuel, but
⁎ Corresponding author.
E-mail address: freitas.flavio@yahoo.com.br (F.A. de Freitas).
https://doi.org/10.1016/j.enconman.2019.112095
ABSTRACT
In this work, waste cupuaçu seeds were calcined for 4 h at 800 °C and evaluated as a heterogeneous catalyst for the biodiesel synthesis. The catalyst (CCS) was characterized by X-ray powder diffraction (XRD), wavelength dispersive x-ray fluorescence (WDXRF), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric and differential thermal analysis (TG-DTA) and soluble alkalinity. The catalytic activity was evaluated by CCS-cat- alyzed ethanolysis of soybean oil and the process was optimized using response surface methodology (RSM) and analysis of variance (ANOVA). The significance of the different process parameters and their combined effects were established through a central composite design (CCD) and the optimum process (catalyst loading of 10% (w/w) relative to oil mass, reaction time 8 h, ethanol:oil molar ratio 10:1 and temperature 80 °C) resulted in a conversion of 98.36% with good agreement with predicted conversion, 97%. The catalyst was recycled, main- taining its great catalytic activity and resulting in conversions close to 98% in the first two cycles. The high potential of CCS as a catalyst for biodiesel production was demonstrated.